Rigid sail construction for boats or the like



Oct. 11, 1949. w. P. CARL, JR 2,484,387

RIGID SAIL CONSTRUCTION FOR 'BOATS OR THE LIKE Filed Aug. 50, 1945 .5 Sheets-Sheet 1 INVENTOR. VV/Lu/g/v P CA/PL, J/P.

' Oct. 11, 1949. w. P. CARL, JR

RIGID SAIL CONSTRUCTION FOR BOATS OR THE LIKE Filed Aug. 30,1945

3 Sheets-Sheet 2 INVENTOR. VV/LL/A/V P CARA, J/P

BY W1, 7 ATTU/P/VYS Oct. 11, 1949., w. P. CARL, .m fi

RIGID SAIL CONSTRUCTION BOATS OR THE LIKE Filed Aug. 30, 1945 3 Sheets-Sheet 3 INIVENTOR. VV/LL/A/V P CA/PL, J/P,

Patented Oct. 11, 1949 UNITED STATES PATENT OFFICE RIGID SAIL CONSTRUCTION FOR BOATS OR THE LIKE William 1'. Carl, Jr., Hampton, Va.

Application August 30, 1945, Serial No. 613,494

6 Claims. 1

This invention relates to sailboats, or the like. and in particular to their sails and the control of said sails.

The art of sailing,-as it exists today, is the result of a very slow evolution from the square sail through the fore and aft gaff-boom rig to the fore and aft Marconi rig. Current conventional sails have several glaring aerodynamic faults:

1. A reat deal of aerodynamic twist.

2. Mast interference.

3. Low critical flutter speed, i. e., when the wind reaches a certain'velocity, the sail will flap like a flag and have to be shortened.

4. Large tip losses, 1. e., when sails are cut in the shape of a triangle, as most conventional sails are, the area near the corners of the sail are not providing as much lift per square foot as they would if a trapezoidal, elliptical or semicircular shape were used.

Other faults of the conventional sailing rig are:

5. The mast is usually stayed at very inefficient angles, throwing tremendous columnar loads into the mast which necessitates a. very complicated system of stays, tending to spring the ship's hull bottom, and induce great loads on the ships sides.

6. The sail must be controlled by ropes through a system of pulleys. Decks and cockpits are cluttered with ropes and cleats.

An object of my invention is to provide a sail construction and control that will eliminate the foregoing defects or faults.

Still another object of the invention is to provide sail structure in which the mast is eliminated as such and in which a substantially rigid sail replaces it that is a self-suflicient hollow structure covered with stressed skin that will take both the bending moments and torsional loads imposed upon it.

Still a further object of my invention is to provide a sail which has essentially a good airfoil section with a part of the trailing portion, approximately thirty per cent of the chord, that may be cambered by flexing or hinging. Hinging the trailing portion makes it possible to change the angle of the trailing portion with respect to the airfoils chord. This effectively cambers the airfoil. By control of this camber, the maximum driving force can be obtained, as is well known.

to aerodynamicists, i. e., a high value of lift to drag ratio is obtainable from an airfoil with a high value of lift.

Another object of the invention is to provide sail structure that can conveniently be folded back into the boat when not in use.

Yet another object of the invention is to provide simple means for controlling camber and the attitude of the sail with respect to the plane of symmetry of the boat so that the sail will trim correctly to any point of sailing and any wind velocity.

To th accomplishment of the foregoing, and such other objects and features as may hereinafter appear, this invention consists in the novel construction and arrangement of parts hereinafter to be described in detail and then sought to be defined in the appended claims, reference being had to the accompanying drawings forming a part hereof, which show, merely for the purposes of illustrative disclosure, preferred embodiments of the invention, it bein expressly understood, however, that changes may be made in practice within the scope of the claims without digressing from the inventive idea.

In the drawings in which similar reference characters denote corresponding parts:

Figure 1 is a top plan view of a boat equipped with the sail of my invention;

Fig. 2 is an elevational view of the boat and sail;

Fig. 2a. is a transverse sectional view on an enlarged scale taken along line 2a2a of Fig. 2 and viewed in the direction of the arrows;

Fig. 2b is a transverse fragmentary sectional view on an enlarged scale taken along line 2b-2b of Fig. 2 and viewed in the direction of the arrows;

Fig. 3 is an enlarged transverse sectional view of the sail of Fig. 2 along line 3-3 thereof and viewed in the direction of the arrows;

Fig. 3a. is a similar view of a modified sail construction;

Fig. 4 is an enlarged section taken along line 44 of Fig. 3 and viewed in the direction of the arrows;

Fig. 5 is an enlarged sectional View taken along line 5-5 of Fig. 2, viewed in the direction of the arrows and illustrating part of the camber control mechanism;

Fig. 6 is a sectional view taken along line B6 of Fig. 5 and viewed inthe direction of the arrows;

Fig. 7 is an enlarged fragmentary top plan view of the sailand camber control; and

Fig. 8 is an elevational view of the same.

Referring to the drawing, l0 denotes a sailboat of conventional construction with which the sail l I of my invention is used.

The sail ll viewed in elevation (Fig. 2) has substantially the trapezoidal form and an airfoil section of normal taper (approximately 2-1) and has a faired tip I 2.

The loads on such a given airfoil are computed for a safe wind and boat velocity in the same manner as for an airplane wing. From the com- Puted loads, the structure is determined. The sail ll includes a shear web l3 which in the embodiment shown has substantially U-section extends longitudinally through the sail in I3 at intervals along its length and extend trans- 1 versely forwardly of the latter. Aft of the shear web I3 and in alignment withthe formers. I5. are ribs I3, cross strips I1 and diagonals I8 preferably of spruce cap strips connected by nonhydroscopic fibreboard gussets I9 01'' the like.

The ribs l and formers 15 when assembled have are attached respectively to a plurality of supports 3|, 3Ia at opposite sides of the trailing end ,of the .cambering portion I.Ia. oi the sail. These cables 3ll,i""3lla', lea d through-suitable openings 32 in the sail cover 23 respectively to hell cranks 33, 33a pivotally supported at opposite sides to the lips I311, I319 of the shear web I3 in the sail.

'pairof buswcabl'es 34, 34a, are connected re- 'spectively to all the bell cranks 33 and all the bell substantially the airfoil sectional shape shown in Fig. 3. It will be noted that the ribs It in their trailing portions are joined together without spacing to form the trailing camberin portion Ila of the sail.

The formers I5 which are plates having the shape seen in plan in Fig. 3 and upstanding side flanges seen in Fig. Qare provided with peripheral recesses 29 in which I-beam section stringers 2I formed from a stressed sectional metallic skin 22 are received and supported. These formers are covered with the sectional stressed skin 22 preferably of aluminum alloy (Ale-lad) or other suitable material whose joints form the stringer 2| and are fastened to the shear web I3. The formers and skin 22 provide a metal stressed skin leading edge for the structure with the skin 22 forming a metallic sheath for the leading edge.

The entire structure is covered with a stressed skin formed of suitable airplane fabric 23 such as Flightex fabric and doped with conventional doping compounds forming the sail I I with its combining trailing portion Ila.

Aluminum alloy (Alclad) gussets 24 (or of other material) are secured suitably to opposite sides of the shear'web l3, the ribs I6 and to the aluminum skin 22 adjacent the root chord I4, overhanging the lowermost edge thereof so that the sail I I may be hingedly mounted toa pivot or rotatable shaft 25in the boat so that the sail may rotate about an axis perpendicularto its airfoil sections.

The shaft 25 runs from the sails root chord It through a bearing 26 of bronze or the like in the deck D of the boat down into a thrust and moment bearing 23 bolted or otherwise secured, for example, to the keel K of the boat II]. A crosshead 21 is fixed to the-upper'en'd of the shaft or pivot 25.. This cross head 21 forms a platform over whose opposite sides the gussets- 24 overhang. The crosshead is provided with spring-loaded oppositely extending horizontal securing pins 28 and 29 which are positioned to extend into openings in the gussets 24 and serveto anchor the sail II to said cross head 21 and hence to the pivot 25. The complete structure of the sail II and shaft or pivot 25 is thus completely cantilevered and the sailmay rotate-about an axis-perpendicular to its airfoil sectionsand' to the boat through a full 360. When it is desired to fold the sail into the boat, it is rotated 180 from the position shown in Fig. 2. Spring loaded pins 29 may then be pressedtoclearthe gussets 24 and the sail rotated about hinge pins 28 as anaxis to the non-use position in theboat. 'At' such time, the cambering portion I la will lie at the top and the leading edge of the sail will then be received in a sail crotch 0 provided intheboat deck. To remove the sail entirely, the spring loaded pins 28 are-also depressed to clear them, from the openingsin gussets24;

The sail II has its portion l'l'a cambered, for

example, in the'followingway. Cables-30, 30a

..cran.k -s .33 a.- -These bus cables lead to a transversely extending drum 35 around which they are wound in oppositerfirections as at 33, 36a so that rotation of drum 35 in one direction tightens one ofth'e' bu's cables and eases off the other 'while itsrotation in the opposite direction has the opposite efiect. The corresponding action of the bu cables 34, 34a alternately tightens or eases off the corresponding cables 30, 30a, causing flexing of portion I Iaand its cambering in the direction of thetightened cables 30 or 39a as shown 'in' Fig 3. In other words, the portion II'a is alternately flexed and ca'mbered to the right or to the left of the normal unflexed full line position of Fig. 3 toward one-'of 'itstwo dotted flexed positions,, depending upon whether cables 39 or 30a have been tightened by the rotation of drum 35 in the required direction.

The drum 35 is supported between the gussets 24 extending outwardly ofthe ail II and extending at one end 35a through a two way or double acting ratchet mechanism 31 to a crank handle 38, the latter for manual manipulation. The two way or double acting ratchet mechanism 31 includes a toothed ratchet wheel 39 rigidly 5 that in a second or neutral position both prongs 42; 43'wili' be clear of said ratchet 'wheel '39- to permit rotation of the-latter and'shaft 35a, and drum 35 in either direction, and so that in a third positiontooth 43 will engage said ratchet wheel 39 to permit rotation of the latter in the opposite direction to that whenpawl 42 engages it and prevents counter rotation.

The pawl 40 may be retained in any of its three mentioned'positions'. To this end, it is provided with the arcuate cam surface 44 having limit stops 45 and 46 at opposite ends. A ratchet control lever 4 is pivotally supported in the gusset 24 and the cover 4'8 of 'thebi-ratchet mechanism". This lev'erAIf is'rnanipulated by a lever 4Ia.- An armor this lever 41a, has a spring loaded pin 49' which bears against the cam surface 44 between the stops 45- 'and 46, so that when lever 41a is rotated in one direction the pin 49 rests against-the stop 46 and forces prong 42 into engagement with the' teeth of ratchet wheel 39. When 49 rests against stop 45, the prong 43 is forced into engagement-with the teeth ofratchet wheel 39. Whenp'in 49 'bears on the cam surface 44 in alignment-with pivot 4|, both prongs 42 and 43 are clear of the teeth of ratchetwheel The two way or double acting ratchet mechanism 31 just described enables one through proper positioning of" its control lever 41a to set it (a) for ratcheting'in"a'clockwisedirection, (b)' for ratcheting'inan anti-clockwise direction, and (c) for'neutral or' disconnection which allows the drum 35 to be turned in either-"direction. The neutral position is utilized for automatic cambering.

An automatic camber control isprovided by extending the handle or crank 38 of drum 35 at 38c (Fig. 8). This extension 38a is adapted-to co-operate with a cam 50 fixed to the "deck D. The cam is concentric with the pivotor shaft 25 and has a depressed portion 50a into which the end of extension 38a projects when the'sail' II lies parallel with the fore and aft direction of the boat. When the sail .II swings out of this position, the end of extension 38a rides out of depression 50a onto surface 501) of the cam and causes appropriate rotation of drum 35 to tighten the corresponding bus cable 34 :or 3411' and effect automatic camberin'g of-the portion Ila. of the sail toward the center line of the boat. Thereafter, if desired, the camber can be increased by flipping the crank 41a to desired 'ratcheting po sition and rotating arm 38further inthe same direction. When automatic camber control alone is desired, the crank-41a is maintained in-neutral position.

The rotation of sail. II about the'axis of the shaft 25 is controllable either manually or automatically. Manual control. is eifected'through lever-like meanssuchas a bull wheel or the like rigidly affixed to the shaft25 and a friction brake of any conventional. form .(not shown). Automatic control is effected either through a rubber bungee cord, or, in the. alternative, by a metal coil spring 54 secured atone end to a hook 55 on the bull wheel 5| andat the other end to a cord 56 which is passed arounda'pulley 51 secured suitably to the. boat. The free end of the cord 55 is attachable to a cleat 58- rigidly secured to the boat so that the cord tension may be adjusted. Any desired variation of spring force can be secured by allowing the cord 56 to wrap around suitably shaped cams (not shown) instead of the bull wheel and by varying its tension When tension is placed in, the cord 56 by tightening up the cord, the sail II is restrained-from revolving in either direction both by the lever arm of the radius of the bull wheel 5| and the tension of the spring 54. Now when the boat I 0 is headed off the wind, the pitching moment on the sail II increases, and, 'byadj i'smi'g thetension for any given strength of wind, the sail II will trim to the proper position. As the boat I0 is headed further off the wind,.the moment of the sail increases proportionately and the. sail will trim automatically to a greater'angle with respect to the boats axis. Thus,. -for anygiven wind velocity, the boat It] can be sailed through a complete circle without touching the sail II. Going about and jibbing' are executed smoothly and without the usual violent'sail flapping.

This control feature has the-following unique advantages over the old conventional method:

1. It does not require constant watchingand control of ropes. V I g I 2. It is a safety feature because if, with a sudden gust, the moment increases on the sail II, the sail automatically changes its angle of attack so as to relieve the heeling moment.

3. It is a more efiicient method of trimming a sail, because, when sailing along and struck with a gust, the immediate change of angle of attack changes what would have been an increased heeling force into a greater driving force.

4. By manual control, the sail can be used as a brake for landing.

5. By manual control, the sail can be positioned so that the boat canbe"sailedb'ackwards; A slightly modified form of sail -I I is shown in Fig. 3a. Therein the cambered portion llaof Fig. 3 is eliminated.- In place thereof, a pivoted trailing flap I la consisting of dope-covered fabric 23a on a frame 60 is hinged suitably 'to the said sail II at 6|, which is the point where the cam-'- bered portion I la of Fig. 3 wouldnormally begin. This flap is equipped with-trailing edge prisms 62 so that the hinge'moment of the flap increases with the angle of attack orin other words-the flap has what is known as a positive iql I which is the ratio of hinge moment coeflicient to angle of attack. When the ratio isnegative, the stability of the sail about the axis around which the sail rotates is increased. Thisfiap Ilav manipulated by the same cable controls used to manipulate cambered portion lid of Fig. 3. All other structural details described for. the sail I I remain the same. In addition, if. desired, the flap Ila could consist of sailcloththat could below-,- ered and raised using conventional trackand slides as desired in the hinged frame 60, which is cable-controlled in the same Way as cambered portionIIaofFig.3.

The structure thus described provides;

1. A rigid sail of. airfoil section and stressed skin construction. I

2. A rigid sail employing no mast.

3. A rigid sail of airfoil controllable camber. I v I 4. A variable controllable camber mechanism that can be either manual orautomaticf 5. A rigid sail which is hinged to a pivot at section with variable the sails root chord for lowering.

6. A control mechanism for maintaining the sail at correct trim for any pointof sailing and any wind velocity, Q I

7. A sail in which the forwardportion is rigid and the rear portion can be dropped.

In addition to the foregoing, a number of other important advantages exist in-my sail constructions. These may be summarized as follows: U

My sail constructions are entirely selfsupporting, and require no haly'ards.

The leading edge of my sail co'nstructions has the stiff metal sub-skin which has as one func tion the prevention of any scallop formation, or any departure from airfoil cross-sectioned configuration, in those portions o'fthe sail between ribs. This is important for efficient sailing. f

In the trailing edge of my sail constructions there is a link provided between ribs, which zire-- vents the covering from cupping or pocketing at the trailing edge.

With the sail constructions of my invention, the cupp d sides of the afterpart of the sail have apositive "Z do: where Ch is thehinge moment and a is the angle of attack, so that the sail tends to float at zero lift, or, in other words, trim and remain in line with the direction of the wind. This is in contrast with sails having, at that part of the sail, a convex section or triangular section, both of which have a negative in which case the hinge moment coefficient decreases with increasing angle of attack, and the 7 float or trim into or againstrthe breeze at positive lift evenrif the sail pivoted ahead of its center rat-pressure. fifhis tends to keep the sail from trimming at zero lift. 1

The trussconstruction in my sails is very effi'cient. The transverse or cross-strips I! do not theoretically take any .load and are very light members used :to halve the unsupported length of the outside frame it which quarters the stress. It-will be noted moreover that the axis of rota tion' of my sail is in. front of the aerodynamic center of pressure of the sail, thereby eliminating any tendency for the boat to upset and so that the sail automatically trims at zero lift. In contrast, in sails which are pivoted behind the aerodynamic center of pressure the sail will not pay out and relieve itself in a breeze but will tend to iine itsel'f up with the boat and upset it. My

is stable while sails pivoted behind the aerodynamic center of pressure are unstable, 1. e., lack weathercock stability. i'While specific embodiments of the invention have "been described, it will be understood that changes-may be made in structural detail within the scope ot'the claims. There is no intention, therefore, 'ofli'mitation to the exact details shown and described. For example, the angle of the axis upon which the sail pivots need only besuch that the sail may, taking into account the characteristics of its cross-section, trim at zero lift, which angle is herein referred to as substantially perpendicular to theboat; and the size and type of the boat hull is immaterial.

I What is claimed is:

1. A rigid sail of symmetrical airfoil section for a boat or the like, having a trailing portionlying in the chord plane of the sail and whose angle with respect to airfoil chord maybe varied, cable means secured to the trailing portion at a plurality of points for trimming the latter to either side of a normal position, sets of pivoted members to which said cable'm'e'ans are secured, and cable ,means secured to said sets of pivoted members for operating the sets in opposite directions to secure effective airfoil cambering in thedesir'ed direction. 2. A rigid sail of symmetrical airfoil section for a boat or the like, having a trailing portion lying in the chord plane of the sail and whose camber or angle with respect to airfoiljchord may be varied, cable meanssecured to the trailing portion at a plurality of points for cambering the latter to either side of a normal uncambered position, sets of levers pivotally supported within the sail and to which said cable means are secured, cable means secured to said sets of pivoted levers for operating the sets simultaneously in opposite directions, and means for actuating said lastnam'ed cable means. 1

3. A rigid sail of symmetrical airfoil section for a boat or the like, having a trailing portion lying in the chord plane of the sail and whose camber may be varied, cable means secured to the trailing portion ata plurality of points for cambering the latter toeitheriside'oi a normal wicambered osition, sets-Inf levers pivotally supported within the sail and to which said cable means are secured, cable means seem-edits saidsets of pivoted levers for operating the sets simultaneously in opposite directions, means for actuating said last-named cable means, doublenacting ratchet means between said actuating means and said last-named cable means for maintaining the :cambering of said trailing portionin desired position, and means for operating said :doubleacting ratchet means.

4: A rig-id-sail of airioil section for a boat or the like, having {a trailing portion whose camber may be varied, cable means secured to the trailing portion ata plurality of points for cambering the latter to either side of :a normal uncambered position, sets of levers pivotally supported within the sail and to whiehsaid cable means are secured, cable means secured to said sets of pivoted levers for operating the sets simultaneously in opposite directions, and cam means for automatically actuatin'g said last-named cablemeans.

5. 'A'rigid sail for a boat or the like, including a shear web, formers secured to the leading side of said web, ribs secured to the trailing side thereof and terminating .camberable trailing portimes, said formers and ribs providing airfoil sections; a-"metallic skincovering the formers to provide a stressed metaliic sheath for the leading edge-of thesail, a fabric covering for the sail overlying the said sheath and said ribs, and means for camberingsaid trailing portions.

6. A rigid: sail for a boat or the like, including a shear web, formers secured to the leading side of the web, ribs secured to the trailing side of said web and terminating in vcarnbe'rable trailing portions, said tori-he rs and ribs providing airfoil sections, a'metallic-skin covering the formers to provide a metallicsheath for the leading edge of the sa'il, a'doped fabric covering for the sail overlyingsaidsheath and: said ribs, cables secured to said 1ibs for flexingthe latter to camber their trailing poriaons, and means for operating said cables. 3

' WILLIAM P. CARL, JR.

.BEFERENCES CITED FQRElGN PATENTS (Io'unt-ry Date GreatBritair-l May 1, 1924 Germany Oct. 22, 1921 Number 198,649- 451,215 

